1. Field of the Invention
This invention generally relates to seals of the type which are utilized for security to provide clear evidence of tampering which include a housing connected to a strap member having an end portion which is receivable within the housing so as to be locked therein and wherein the strap or housing is severed or damaged to provide a visual indication of tampering in the event any action is taken to remove the end portion of the strap from the housing. More particularly, the present invention is directed to tamper-resistant security seals of the type in which a shackle has an end portion insertable within two or more locking cages supported within a housing in such a manner that two of the locking cages cooperate to prevent withdrawal of the strap unless sufficient force is applied to destroy a portion of the shackle strap or the housing to thereby provide a clear indication of tampering.
2. History of the Related Art
Tamper-indicating shackle seals are widely used where it is necessary to ensure that there has been no unauthorized entry or access obtained into secured areas. Such areas may include the contents of shipping containers, mail pouches, shipping bags, cargo trucks, international shipping containers and the like or may include meters, valves, storage areas, buildings and the like. Among the requirements for such seals is that they be easy to use, that they function readily to give a visual indication of unauthorized tampering of the seals and that they are inexpensive. One piece plastic seals are commonly used in a variety of industries in that they are easy to stock, are non-corrodable, are easy to place into service and are easily removable by authorized personnel when service is no longer required. Further, such seals are easy to stamp to provide identication to a specific seal placed into service for a specific use.
It is important, however, that tamper indicating seals must be durable enough to withstand ordinary handling, especially those which are utilized in the shipping and cargo industries. Ultimately, however, the value of such seals is determined by whether or not the structure of the seals provides a positive indication that no tampering has occurred. Therefore, such seals must give a visual indication of tampering in the event an unauthorized opening of a seal has been made.
The use of tamper indicating shackle seals which include a plastic housing having internal spring-like fingers which engage portions of a shackle or strap integrally formed with the housing is well known. Such seals must be designed so that the spring-like fingers of the housings engage the shackle or strap securely so that the shackle or strap cannot be withdrawn from the housing without physically damaging the housing or the strap. Most conventionally, the seals are designed so that a portion of the strap will sever, perhaps along a line of weakness or opening created in the strap, if force is applied to withdraw the shackle or strap from the housing. In other conventional structures, a portion of the housing may be designed to shatter or be distorted to give a visual indication of tampering when there has been an application of pressure or force to withdraw the shackle or strap from the housing. In yet other structures, a portion of the seal may become discolored by the application of force to the shackle or strap to thereby give a visual indication of tampering.
One drawback with some conventional plastic seals formed of polyethylene or polypropylene is that, through the application of heat, the material of the seal may be softened to a point where the shackle may be manipulated sufficiently to withdraw it from the housing without giving a permanent indication that such removal has occurred. This would allow access to the sealed contents of an enclosed area after which the seal could be reassembled.
To overcome this situation, developments were made wherein the locking fingers within the seal housings were separately molded of resinous material exhibiting a greater resistance to increased temperatures, such as nylon. Such structures not only allowed for a reduction in molding costs but also provided internal locking elements which could not be bypassed by the application of heat. See for instance, U.S. Pat. No. 5,056,837 to Fuehrer.
Other tamper indicating shackle seals have been designed to provide increased locking engagement between the housing and the shackle or strap of the seal. In British Patent No. 2,164,003 to Yap, a security seal is disclosed which includes a pair of internal locking members for engaging spaced locking elements or teeth associated with a strap. The seals are manufactured of a polypropylene or other material which displays evidence of tampering by changing color at points along the seal where stress is applied. Unfortunately, such a seal suffers from the shortcomings of other polypropylene seals with respect to the application of heat.
Many prior art tamper indicating shackle seals having a single inlet opening into a housing whereby the opposite end of the housing is sealed either integrally with the housing or by providing a separate plug. This type of structure prevents access into the area of the locking teeth of the housing through an end opposite the inlet end of the housing. However, in some instances, it is not possible to utilize closed end housings, especially where the seals must be drawn tightly around an object being secured such as the opposing handles of a closure or the neck of a flaccid container such as a mail pouch or bag. In these instances, both ends of the housing of the security seal must be open.
It has now been determined that in some instances, plastic tamper indicating shackle seals may be subject to tampering through the application of a freezing medium or a cooling spray which acts to harden the locking teeth in an open position. By urging the shackle or strap inwardly of the housing, the locking elements of the strap will expand the spring-like fingers within the housing to their maximum degree. At this point, if a coolant is applied to the housing to fix the spring-like fingers in an expanded position, in some instances, it is possible to actually withdraw the shackle from the housing to gain access to a restricted object or area.
In view of the foregoing, there is a need to ensure that tamper indicating shackle seals can be designed in such a manner that they cannot be tampered with by heating or cooling of the seal components.